This invention relates to a display apparatus. In particular, it relates to a display apparatus capable of sequentially displaying a plurality of static images, such as advertising images.
Display apparatus of this type is extensively used in advertising, especially at the point of sale or on billboards for example. A typical prior art example of an advertising medium capable of presenting more than one image sequentially comprises an array of elongate elements which are triangular in cross-section. Parts of the whole image are provided on each of the elongate faces so that when one set of these face outward a viewer can see an entire image disposed across all the faces. After a time period, each of the element rotates about its longitudinal axis to bring another face forward to view a second image. Such a system therefore enables three different images to be viewed, each for a predetermined period of time.
Such devices are, however, bulky and have a large depth because of the depth required by the triangular section pieces. Also, since advertisements are changed and updated regularly, it can be difficult to change an advertisement since this requires altering the image on each of the three faces on each of the triangular pieces. This can be very time consuming where a large number of triangular pieces are provided to form each image. For example, twenty separate triangular pieces may be laid continuously to form a single image.
Attempts have been made to reduce the complexity of such devices and to overcome the complexity of rotating members by using planar sheets. Examples of these are shown in U.S. Pat. Nos. 2,141,393, 3,403,465, 3,421,240 and 3,659,367. Each of these relates to a changeable display structure comprising a plurality of slatted sheets which are interleaved such that relative sliding movement causes images to be selectively exposed to view. Often, as in U.S. Pat. Nos. 2,141,398 and 3,659,367 these devices are intended for manual manipulation and are therefore of limited use. Attempts to drive the sheets, by means such as motors, have often tended to complicate their structure, as in U.S. Pat. No. 3,421,240. Also, in prior art devices it has generally been difficult or time consuming to change messages. Training, and therefore skilled personnel, is often required to change the messages displayed.